ISGDGRSRES — Display Global Resource Serialization Resource Exit

ISGDGRSRES is called for each ENQ resource displayed in a DISPLAY GRS,RES= or CONTENTION command. It allows an application to provide additional information describing the meaning of the ENQ resource name.

The parameter list passed to ISGDGRSRES is mapped by ISGYDSPX (DSPX). The parameter list describes an ENQ resource name.

Replacing the Exit Routine

For information regarding dynamic exit routine replacement, see Replacing a Dynamic Exit Routine.

Exit Routine Environment

ISGDGRSRES receives control in the following environment:

Enabled for interrupts.
In supervisor state with PSW key 0.
In primary mode with H = P = S = requestor's address space.
In AMODE 31 and RMODE ANY.
With no locks held.
An EUT FRR is held when the exit routine is called.

Exit Recovery is as follows.

If an error occurs, ISGDGRSRES provides with its own recovery routine.
If no recovery exists, or the recovery continues with termination, GRS fails the request and continues processing. CSVDYNEX rules for the exit are used to determine whether the exit should be removed.
The unplanned removal of an exit can result in serialization changes. Such changes might cause data integrity errors. Therefore, it is important to provide recovery and to understand how CSVDYNEX determines when to remove an abend exit. For more information about CSVDYNEX, see z/OS MVS Programming: Authorized Assembler Services Reference ALE-DYN.

Exit Routine Processing

The exit routine should interrogate the QNAME and RNAME information that will be displayed. If the exit routine can add information about the meaning of the QNAME and RNAME for the resource, it can place:

An identifier (16 EBCDIC characters padded with EBCDIC blanks on the right, if needed) in the Dspx_ResourceIdentifier field (for example, a subsystem or product name).
Descriptive information (up to 70 EBCDIC characters padded with EBCDIC blanks on the right, if needed) in the Dspx_ResourceInformation field.

For an example, see Providing ENQ resource information on DISPLAY GRS in z/OS MVS Programming: Authorized Assembler Services Guide.

Programming Considerations

Observe the following conventions when coding a display global resource serialization exit routine:

Every exit routine must be reentrant.
Be aware while coding the exit routine that because the exit is called for every resource displayed in a DISPLAY GRS command response, excessive path length could degrade system performance.
Do not code the exit routine to issue the WAIT macro or call a service, such as WTOR, that issues a WAIT.
Do not code the exit routine to issue another ENQ, RESERVE, or DEQ macro.

Entry Specifications

The system passes a ISGYDSPX parameter list (DSPX) to the exit routine. The DSPX contains the QNAME, RNAME, and scope of the resource being displayed. The exit routine can update the resource identifier and information fields for display.

Registers at Entry: The contents of the registers on entry to the exit are as follows.

Register: Contents
0: Not applicable
1: Address of the exit parameter list (ISGYDSPX)
2-12: Not applicable
13: Address of a 72-byte save area
14: Return address
15: Entry point address of ISGDGRSRES

Parameter List Contents: Register 1 contains the address of the exit parameter (DSPX) that is mapped by macro ISGYDSPX. Refer to z/OS MVS Data Areas in z/OS Internet Library at http://www.ibm.com/systems/z/os/zos/bkserv/ for the mapping of the ISGYDSPX data area.

Return Specifications

The information displayed in the command output will be that from the last exit routine to update the DSPX parameter list.

Registers at Exit: Upon return from the exit processing, the register contents must be as follows.

Register: Contents
0-14: Restored to contents on entry
15: 0